Conventionally, a gas analyzing apparatus configured to measure a concentration of a component in an exhaust gas generated from a flue, etc. using a chemical luminescence analysis (CLA) method has been known.
For example, Japanese Patent Application Publication No. H7-301603 discloses a CLA type nitric oxide measurement apparatus comprising a pump, a flow controller, a flowmeter, an ozone generator, a smoothing device, and an ozone flow path configured both to supply ozone and to supply a dilution air into a reaction chamber. In this gas analyzing apparatus, a flow rate of the ozone flow path is adjusted appropriately to dilute a luminescence interfering gas such as CO2, etc. and a concentration of ozone is optimized to maximize detection sensitivity of chemical luminescence in accordance with a concentration of nitric oxide in the sample gas. In addition, in this gas analyzing apparatus, a high voltage power source configured to drive the ozone generator is controlled by a pulse-width-modulation type concentration setting unit. Furthermore, in the CLA type nitric oxide measurement apparatus disclosed in Japanese Patent Application Publication No. H7-301603, a section where a concentration of ozone is set to zero is introduced when generating ozone intermittently and a measurement system (a light detector and its amplification system) for measuring intensity of chemical luminescence is calibrated in the section where the concentration of ozone is zero. Thus, high sensitivity amplification can be achieved.
However, a gas analyzing apparatus using CLA method using an ozone generator configured to generate ozone (O3) by electric discharge cannot measure, with high accuracy, a concentration of a predetermined component to be measured in the sample gas, especially when the concentration of the predetermined component is low, such as a concentration of a few parts per million (ppm).